Coasts Flashcards
1
Q
What is a high energy environment?
A
exposed coasts, facing prevailing winds with long wave fetches resulting in powerful waves.
where the rate of erosion exceeds the rate of deposition
They create rocky coasts
2
Q
What are some landforms that are created in high energy environments?
A
Headlands
Cliffs
Shoreline platforms
3
Q
Name a high energy environment
A
Coasts facing the Atlantic where the waves are powerful all year - Cornwall
4
Q
What is a low energy coastline?
A
Coasts where the waves are less powerful or where the coast is sheltered from large waves
The rate of deposition exceeds the rate of erosion
Sandy and estuarine coasts found
5
Q
What are some landforms that are created in low energy environments?
A
Beaches
Spits
Coastal plains
6
Q
What is the coastal system?
A
The process of the changing coastline which is constant
7
Q
Inputs for the coastal system
A
Marine - waves, tides, storm surges
Atmospheric - weather, climate
Terrestrial - Rock type, structure, tectonic activity
People - human activity, coastal management
8
Q
Processes at the coastal system
A
Weathering Mass movement Erosion Transport Deposition
9
Q
Outputs at the coastal system
A
Erosional landforms
Depositional landforms
Types of coasts
10
Q
Structure of land in north and west
A
Rocky coasts harder older rock resistant to Atlantic erosion rocky coastline can withstand storms High energy coastlines
11
Q
Types of rocks in the north and west
A
Igneous rock - basalt and granite
Older compacted sedimentary rocks - old red sandstone
metamorphic rocks - slates and schists
12
Q
Structure of land in south and east
A
Weaker and younger sedimentary rocks - chalk, clay, sandstone
Mostly low lying sanding beaches
Low energy environments
13
Q
Example of coastal plain
A
The Wash - area of low, flat relief
Largest estuary in UK
Tidal creeks, mudflats, salt marshes, lagoons
14
Q
Littoral zone
A
the boundary between the land and sea
15
Q
Order of littoral zone - land to sea
A
Back shore, foreshore, near shore, offshore
16
Q
Which area of the littoral zone are effected the most?
A
Back shore and foreshore - They experience the most changes as it is where the most human activity occurs
17
Q
Back shore
A
usually above influence of waves
18
Q
Foreshore
A
Inter-tidal or surf zone
19
Q
Nearshore
A
Breaker zone - zone of breaking waves
20
Q
Offshore
A
Beyond influence of waves
21
Q
Why is the littoral zone constantly changing?
A
due to dynamic interaction between sea processes
22
Q
Long term factors of changing littoral zone
A
Changes in sea level
Climate change
23
Q
short term factors of changing littoral zone
A
Individual waves
daily tides
seasonal storms
24
Q
How can be coasts classified?
A
Geology
Formation processes
Balance of erosion and deposition
Sea level change
25
How can be coasts classified? - geology
Rock type and structure can create rocky/sandy/concordant/discordant
26
How can be coasts classified? - formation processes
Primary coasts - land based processes (river deposition)
| Secondary coasts - marine based processes (wave action)
27
How can be coasts classified? - balance of erosion and deposition
Erosional or depsotional coasts
28
How can be coasts classified? - sea level change
submergent or emergent
29
Different sediment supplies
Cliff eroding
tidal current which picks up glacial deposits from shallow sea floor
from other coasts
Rivers discharge into coastal area
30
Sediment cells
Created when sediment comes from two directions from North and East
31
Strata
layers of rock
32
Bedding planes
These are natural breaks in strata, caused by gaps in time during periods of rock formation (horizontal cracks)
33
Joints
These are fractures, caused either by contraction as sediments dry out or by earth movements during vertical uplift
34
Folds
Formed by pressure during tectonic activity, makes rocks buckle and crumple
35
Faults
Formed when stress or pressure to which a rock is subjected, exceeds its internal strength, causing it to fracture - the faults then move or slips along fault plains
36
dip
the refers to the angle which strata lie - horizontally, vertically, dipping towards or away from sea
37
Cliff profiles - marine erosion dominated characteristics
Steep face
Active undercutting
Limited cliff base debris - as it is quickly broken up by erosion and carried away by waves
unvegetated
38
Cliff profiles - sub-aerial processes dominated characteristics
Shallower curved slope profile, lower relief
low angle
accumulated debris
sub-aerial processes of surface run-off erosion and mass movement
debris not removed due to low marine wave erosion
39
Cliff profile
The height and angle of a cliff as well as its features, such as wave-cut notches or changes in slope angle
40
Characteristics of a coast with cliffs
Transition from land to sea is abrupt
Low tide = foreshore is exposed as a rocky platform
cliffs are vertical
41
Characteristics of sandy coastline
High tide = beach is inundated, vegetated dunes aren't
| Dune vegetation stabilises the coast and prevents erosion
42
Characteristics of estuarine coastline
```
Found at the mouth of rivers
extensive mudflats, cut by channels
Low tide = exposed
High tide = inundated
Back shore's mudflats are vegetated
Coastline transitions from land to sea
```
43
Geological structure
Refers to how the rock is arranged on macro scale. it looks at the arrangement of different rock types in relation to each other
44
Concordant coastline
Rock is parallel to the coastline
| Straight coast with development of coves
45
Discordance coastline
Rock is perpendicular to coastline
| Headlands and bays
46
Explain how headlands and bays are formed
Discordant coastline there are layers of hard and soft rock perpendicular
wave action erodes less resistant rock quick due to abrasion and HA = bays
More resistant rock is left = headlands - this causes incoming waves to refract as water becomes shallower (wave refraction)
wave energy is now concentrated on the headland
wave becomes higher and steeper increasing erosional power
bay is sheltered as wave energy dissipated - beaches form
47
In theory what may happen overtime to headlands and bays?
Headlands will be eroded to become caves, arches, stacks. The coastline may even out before the process starts again
48
Coastal morphology
The shape and form of coastal landscapes and their features
49
Coastal recession
Coastal erosion
50
Horizontal starta creates..
steep cliffs
-recession rates are quicker when soft layer bottom
cliff retreat is exposed to the sea
fairly stable profile
51
cliff profile - rock dips gently towards the sea, almost vertical points
joints opened up by pressure and release and weathering
| slight seaward dipping bedding planes can increase recession rates due to mass movement and weathering
52
cliff profile - steep dips towards sea
rock slabs slide down the cliff along bedding planes
| seaward dipping bedding planes can be unstable this increases recession rates
53
cliff profile - rocks dip inland producing a stable, steep cliff profile
landward dipping bedding plane
steep and stable
this can decrease recession rates
54
cliff profile - rock dips inland but with well-developed joints at right angles to bedding planes
joints act as slide planes - this can increase recession
55
meso
medium
56
micro
small
57
macro
large
58
Geological structure on meso scale
sedimentary tend to be in clear defined layers
59
Geological structure on micro scale
some rock types are more likely to have joints and bedding planes
60
Most resistant rocks (igneous)
crystalline structure - interlocking crystals
-well-connected, impermeable, joints
create rocky coastlines with steep cliff profiles that erode slowly
igneous rocks like granite recession rates = 0.1-0.3 cm/yr
61
Resistant metamorphic rocks
well connected and impermeable
folded and faulted so have weaknesses
create rocky coastlines with steep cliff profiles
marble, schist, slate erosion rates = 0.5-1cm/yr
62
Resistant sedimentrey rock
limestone and chalk are relatively resistant but are more vulnerable as they are clastic
-made up of cemented sediment particles rather than interlocking crystals
-formed in strata with joints providing weaknesses and makes limestone permeable
chalk is porous as there are air spaces between particles
Form steep cliffs, headlands and wave-cut platforms
LS = 1-2cm/yr
chalk = 1-100cm/yr
63
Less resistant rocks - unconsolidated
often layers of impermeable rock where water can remove cement between particles
high pore water pressure can reduce stability
unconsolidated rocks have not been cemented together by pressure
sandstone = 10-100cm/yr
boulder clay - left by glaciers - least resistant as it is lose and not cemented together = 100-1000cm/yr
stepped/slumped coastlines due to slumping
64
Factors affecting the rate of coastal recession
Geology and lithology
weathering and mass movement
wave energy
absence of beach
rising sea levels
human intervention - coastal management, development
marine processes- fetch, destructive waves, lsd, sub aerial processes
65
How are coves formed?
```
concordant coastline - waves are parallel to sea
destructive waves
destructive waves hit coastline in winter - HA and abrasion
attacks weaknesses (joints and faults) in resistant limestone
eventually erosion slows down as more resistant chalk layers are met and cove has been made.
```
66
Dalmatian coasts
tectonic activity folded limestone layers so that ridges (anticlines) and valleys (synclines) formed parallel to the coast
Sea level rose due to end of ice age and drowned the valleys creating a submergent coastline
The ridges remain as islands running parallel to the coastline
67
Haff coasts
Form on concordant coastlines
Long sediment ridges topped by sand dunes that run parallel to the coast
The build of these sand dunes have created lagoons between them and the shore
Form in low energy environments where deposition occurs but onshore winds and low energy waves
- Baltic Sea
68
factors affecting shape of the coastline
rocks and sediment
| vegetation
69
How does vegetation help stabilise unconsolidated sediments at the coast and reduce erosion?
Marram Grass - xerophyte
| Glasswort - halophyte
70
How do Marram Grass stabilise sediment?
Deep roots
Capture blown sand making it ideal for stabilising shifting dunes
Growing conditions
71
How do Marram Grass stabilise sediment? - deep roots
```
3m deep roots help to bind sediment together making them less vulnerable to wind and water erosion - they reach down in search of moisture
creeping stems (rhizomes) extend widthways, sending down even more like ladder structures
```
72
How do Marram Grass stabilise sediment? - growing conditions
Grows in conditions, free-draining sand - helps to prevent unnecessary water loss
73
where are marram grass?
sand dunes - xerophytes
74
Where are glasswort?
salt marsh - halophyte
75
How do Glasswort stabilise sediment?
- submerged
- stem
- dead organic matter
- salt resistant
76
How do Glasswort stabilise sediment? - submerged
-when submerged, plants provide a protective layer so that the sediment is not directly exposed to erosion by the tide
77
How do Glasswort stabilise sediment? - stem
it has a succulent stem so it stores water
78
How do Glasswort stabilise sediment? - dead organic matter
dead organic matter is added to the sediment and helps to create soil which is less vulnerable than loose sediment
79
How do Glasswort stabilise sediment? - salt
salt resistant - protected against water erosion
80
sand dune
psammosere
81
Salt marsh
halosere
82
Succession
refers to the changing structure of a plant community over time as an initially bare surface is colonised by pioneer species and continues to develop
83
What kind of coastlines does plant succession occur on?
coastlines where deposition takes place
| low energy environments that are sheltered from high energy waves
84
Fetch
the distance over which the wind has blown
| - south coast has the largest fetch (Devon and Cornwall)
85
How are waves created?
As wind blows over the ocean, friction occurs and energy is transferred to create a wave
The stronger the wind = the greater the wave power
86
What factors affect the energy of waves?
wind speed
distance
time
fetch
87
As the wave gets closer to the shore...
the wave length decreases
| the wave height increases
88
Describe the movement of the wave
Waves move across the open ocean in a circular motion as ocean swell
As they reach shallower water, the frictional drag on the sea bed slows down the base of the wave
Eventually the wave breaks as the top of the wave is moving faster than the base
89
What is a swell wave?
is an ocean waves system raised at some distance away due winds blowing there
90
Where are swell waves formed?
Travel out of a stormy or windy area that have travelled from their fetch and continue on in the direction of the winds that originally formed them as sea waves
91
What happens as the swell advances?
its crest becomes flattened and rounded, smoothed surface
92
Do swell waves follow the prevailing winds?
They come from different directions than normal prevailing winds and sea waves
Sometimes come from the same direction making it hard to distinguish the two different systems
93
When is marine erosion at its highest?
Winter season as they produce destructive waves
94
What are landforms of coastal erosion?
```
Headlands and bays
Coves
Caves, arches
Cliffs
Blowholes
```
95
Simple - how are cave, arch, stack, stump formed?
| Example
Wave refraction concentrates wave action on the headland
Hydraulic action and abrasion slowly erode the headland to form a series of headland
e.g. Old Harry's Rock
more on folder
96
Simple - how are blowholes created?
Caves can potentially collapse to produce a hole in the cliff
Waves hitting the base of the cliff can be forced through and spout water at the top
97
How are wave cut platforms formed?
- wave action at the base of the cliff means that hydraulic action and abrasion undercuts the cliff to form a wave cut notch
- continues and the cliff above the notch is left unsupported and eventually collapses
- cliff retreats leaving wave cut platform which is the base of the cliff that is left
- this process maintains steep cliff profiles
98
Beach morphology
the shape of a beach, including width and slope profiles and other features such as berms
99
Beach morphology - What happens to it during summer?
Deposition exceeds erosion
Creation of a berm
Slopes
during summer, sediment is returned by constructive waves
100
Beach morphology - What happens to it during winter?
```
Erosion exceeds deposition
Dune erosion
Berm erosion
Bar formation
Steep cliff
during winter, sediment is dragged offshore by destructive waves
```
101
Beach morphology - how does material change along a beach?
- beaches consist of lose material so morphology changes as waves change
- material along a beach profile also varies in size and type depending on distance from the shoreline
102
Describe a beach profile in summer
- beach is steeper when there are more constructive waves
- constructive waves are less frequent (6-9 per min) so wave energy dissipates and deposits over a wide area
- the swash of constructive waves deposits larger material at the top of the beach creating a berm
- as the berm builds up, the backwash becomes weaker due to draining through percolation rather than down the beach
- beach material becomes smaller towards the shoreline
103
Describe a beach profile in winter
- Destructive waves occur at a higher frequency
- berms are eroded by plunging waves and high energy swash
- strong backwash transports sediments offshore depositing it as offshore bars
- sometimes the backwash exerts a current known as a rip or undertow
- this drags the sediment back as the next wave arrives over the top
104
What are the factors that influence beach morphology?
- Sediment supply from river is reduced
- Interference in sediment supply along the coast
- Climate change
105
What are the factors that influence beach morphology? - Sediment supply from river is reduced
Due to construction of dams on rivers that traps sediment upstream
106
What are the factors that influence beach morphology? - Interference in sediment supply along the coast
Coastal management
107
What are the factors that influence beach morphology? - Climate change
increase in storms, destructive waves, erosion
108
Beach profile in storm beaches
high-energy deposition of very coarse sediment
109
Beach profile in the middle of beach
mostly sand but sand is more coarser where berms/ridges have been deposited than in channels or runnels
110
Beach profile of offshore
offshore ridges and bars are formed by destructive waves erosion and subsequent deposition of sand and shingle offshore
111
Cavitation
causes air in cracks to expand and forces cracks open
112
Why is sediment constantly moving? 3 factors
waves, tides and currents
LSD
traction, saltation, suspension
113
Traction
large sediment rolled across seabed
114
Saltation
Medium load bounced
115
Suspension
Fine load taken along
116
Describe the process of long-shore drift
- prevailing winds approach coast at an angle
- swash moves sediment up beach at 45degrees and backwash moves 90 degrees down under gravity
- traction, saltation and suspension
- sediment is moves east and over time a drift aligned beach is formed
- sediment experiences attrition and abrasion becomes smaller and more rounded
117
What is a swash aligned beach?
- waves approach the coastline perpendicular to the beach
| - the swash and backwash move sediments up and down the beach creating a stable and straight beach
118
What is a drift aligned beach?
- waves approach at an angle and sediment is moved along by long-shore drift
- creates wide beaches but uneven sediment spread
119
What are the sources of sediment?
- rivers
- constructive waves from seabed
- cliff erosion
- LSD transports sediment
120
Why does deposition occur?
- deposition in low energy coastal environments occur due to gravity
- coarse sediment drops first, finer is further away
- flocculation helps deposition of fine clay particles that are very light
- these clump together in salt water making them heavier
121
What stabilises deposited sediment?
Vegetation - salt marsh, sand dune succession
122
Describe the formation of a spit
- lsd moves sediment along
- lsd continues as there is a change in the direction of the coastline
- waves lose energy in the slacker behind the headland and large sediments are deposited
- as deposition occurs, spit forms
- finer material is carried further along the spit before being deposited as it is lighter
- flocculation helps to settle fine clay
- when the rivers current stops deposition across the estuary preventing a bar from forming
123
What happens when there is no river currents during the formation of a spit?
when there is no river currents preventing long shore drift depositing in a straight line across so the spit eventually joins the land to create a bar
124
Example of a spit
Spurn head, Chesil Beach
125
Example of a bar
Slapton Sands, Devon
126
Describe the formation of a tombolo
- an island joined to the mainland
- it develops when deposition occurs behind an island due to the low energy environment
- eventually the island becomes connected to the mainland
- also by lsd and a bar forming
127
Example of a tombolo
St Michaels mount, Cornwall/ Chesil Beach
128
Describe how double spits and cuspate forelands are formed
- LSD happens from both directions, leading to 2 spits forming and meeting up -cuspate forelands
- deposition occurs in the slack water behind to create the distinctive shaped coastline
129
Examples of double spits and cuspate forelands
Dungeness, Kent
130
Describe how barrier islands are formed
- an offshore sand bar thought to have formed when a plentiful supply of sediment was deposited in sand dunes along the eastern seaboard of the USA by waves and winds
- as sea levels have risen, land behind was flooded to create a lagoon but the sand dunes themselves become elongated islands running parallel to the coast in USA
- as sea levels rise, they migrate inland
- they provide protection to the coastline during storms as they absorb wave energy
131
Describe how offshore bars are formed
- a long ridge of sand and pebbles found a short distance out to sea
- forms in shallow water offshore where slope is gentle
- following a large erosion event during a storm
- beach and sand dunes can be scoured heavily by destructive waves
- extra sediment is deposited vertically offshore in a bar
- these offshore bars may only be temporary
- LSD can add to them or change their shape
132
Sediment cell
an area of a coastline that acts like a closed system
| -there are sources, transfers and sinks within each cell
133
How many cells is the Uk split into?
| what are cells?
11 sediment cells
length of the coastline that are relatively self contained boundaries which are often natural boundaries e.g. headlands
-each sediment cell is clones when there are large barriers between them with little transfer between them
134
What are cells split into?
split into sub cells
they are managed at a local level by an SMP (shoreline management plan)
-under certain conditions transfers between the main sediment within the cell takes place
135
Name the sources of the cell system
- wind-blown sediments from land
- erosion of cliffs
- onshore currents supplying sediments to the shore
- land sediments eroded by rivers
- sub-aerial processes (weathering and mass movement)
- shells and remains of marine organisms
136
Name the transfers of the cell system
```
LSD
wave transport - swash and backwash
tides moving in and out
currents- localised (rip) or large scale
wind along shore or on/offshore
```
137
Name the sinks of the cell system
```
Sand dunes
Offshore bar
back depositional landforms
Foreshore depositional landforms
nearshore depositional landforms
offshore sediment deposition to deep offshore water
```
138
what is a sediment budget used for and why are they useful?
- the amount of sediment gained from sources and lost to sinks can be and called a sediment budget
- they are useful in assessing coastal change and the effects of coastal management schemes
139
What is a sediment budget?
the amount of sediment gained from sources and lost to sinks can be quantified
inputs from sources - outputs to sinks
140
What happens if the sediment budget is negative?
The coastline starts to degrade - erosion
141
What happens if the sediment budget is positive?
The coastline starts to aggrade - accretion
142
What happens if the sediment budget falls?
There is more loss to sinks that gained from sources
| Therefore there may be more erosion from sources to balance the budget
143
What happens if the sediment budget increases?
There is more gain from sources then loss to sinks
| Therefore more deposition in sinks
144
What state are sediment cell systems in?
in a state of dynamic equilibrium
145
What is negative feedback?
Usually helps to maintain a balance within the system
146
Example of negative feedback?
E.g. Wave erosion causing rocks falls which then protects the base of a cliff from further erosion
147
What is positive feedback?
Works to increase the erosion of coast and increases the source of sediment
148
Example of positive feedback?
E.g. Damage to sand dunes during storm conditions, which may create a 'blow out' allowing the wind to move sand away, preventing grass from regrowing, therefore further erosion occurs
149
How has the Holderness Coastline in Northern England been affected by climate change?
- storms in a year can remove 7-10m of coastline
- weak clay, stormy nature of the North Se, rising sea levels of 4mm a year
- slumping
150
Sub aerial processes
refers to the processes of weathering and mass movement
| -processes that occur on the cliff face rather than the cliff foot
151
What is weathering?
the breakdown of rock in situ by mechanical, chemical or biological agents
152
What is erosion?
the breakdown and removal of rock by an external agent (wind, waves, rivers, ice)
153
What is mass movement?
the movement of rocks/sediment downslope due to gravity - weathering processes can help this happen
154
What factors might influence how vulnerable a cliff is to mass movement?
- lithology and structure of a cliff can determine which mass movement it is vulnerable to
- weathering processes can contribute to the loosening of cliff faces so that mass movements are more likely
- rainfall is often a cause of mass movements
- angle of the slope
155
Name the different types of mass movement
```
Landslide
Slump
Mud/earth flow
Rock fall
Debris slide
Soil creep
```
156
Describe how a landslide occurs
Rocks that are jointed or have bedding planes that are parallel to slope or cliff surface are susceptible to mass movement
-increase water, lack of friction will increase sliding
157
Describe how slumps occur
Occur is saturated conditions
- rotational movement
- moderate/steep slopes
- soft materials (clay and sand) overlies more permeable rock which causes rotational scars
- repeated slumping creates a terrace cliff profile
158
Describe how mud/earth-flows occur
increase in water can reduce friction causes earth and mud to flow under the underlying bedrock
159
Describe how rocks falls/ debris slides occur
- occur on strong joints rock faces which are exposed to mechanical weathering
- occurs on slopes over 40 degrees
- material bounces or falls vertically to form scree/talus
160
Describe how soil creep occurs
- very slow downhill movement of individual particles
- continuous process
- slowest form of mass movement
161
What is a eustatic sea level rise?
When the sea rises and falls by itself
-sea changes relative to land (global) as ice melts from ice caps and glaciers and thermal expansion or forms according to global climate and the cycle glaciers or inter-glaciers
162
What creates a eustatic sea level rise?
tides
ice ages
storm surges
hurricanes
163
What creates an isotonic sea level rise?
when the land changes relative to the sea
| -the land rises and falls by itself (local)
164
what creates a eustatic sea level rise?
Isotonic rebound - large amounts of ice pressed down on land in the last ice age and now these land masses are rising
165
What is an isotonic rebound?
large amounts of ice pressed down on land in the last ice age and now these land masses are rising - glacial rebound
166
In relation to the tees - ex line, where is the low land and is it rising or sinking isotonically?
The lowland in the UK is sinking, this is the South and East UK
167
In relation to the tees - ex line, where is the highland and is it rising or sinking isotonically?
The highland in the UK is rising, this is the North and West UK
168
What factors affect sea level?
Tectonics
Accretion
Sub-mergent coastline
Emergent coastline
169
How do tectonics affect the sea level?
land can be pushed by plates in a series of earthquakes
- new islands can rise out of the sea in eruptions
e. g. Surtsey, Iceland
170
How does accretion affect sea level?
this is the deposition of sediment
- in a river estuary or delta, this can weigh down the crust and also causes sinking (subsidence)
e. g. Thames estuary
171
How does a submergent coastline affect sea level?
| examples
It is produced by a eustatcic sea level rise
| e.g. Fjords, Rias, Dalmatian coasts
172
How does an emergent coastline affect the sea level?
produced mainly by isotonic readjustment/rebound
includes relict/fossil cliffs and raised beaches
e.g. Vik, South Devon
173
What are fjords?
they are drowned glacial u shaped valleys
174
how are fjords formed?
- large glaciers formed huge u-shaped valleys during the ice age that went well all the way into the sea
- the erosive power of the ice eroded deeper then sea level
- at the end of the ice age, eustatic sea level rise drowned the valleys to create spectacular fjords
- have a submerged lip at the Seward end of the fjord where the glacier need and left a terminal moraine
- post glacial isostatic rebound is occurring in many areas where fjords are present, slowly lifting them up from sea level, making them shallower by a few mm a year
175
what are rias?
drowned river valleys that were not glaciated in the last ice age.
176
how are rias formed?
- before the end of the last ice age, a small river with its tributaries met the sea
- when sea levels rose eustatically, the main channels and its tributaries and the floodplain were drowned and the sea advanced inland
- this created an estuary at the mouth that is larger than the original river valley
177
How are emergent coastlines formed?
- at the end of the last ice age, the ice melted and the land that was covered started to rebound slowly as the huge weight was removed
- this meant that beach platforms rose out of the sea to become new land (raised beaches) and their cliffs also rose to become stranded above the current sea level
- as the raised beach is no longer a beach, sediment is slowly removed by wind, rain and rivers
- the relit cliff may still display features like caves and stacks
178
What does IPCC stand for?
Intergovernmental panel on climate change
179
What is IPCC?
an international organisation of scientists, created by the united nations, from around the world who monitor climate change and creates climate models
180
What are the two main causes of sea level rise?
- as water heats up, it takes up more room
| - as glaciers and ice sheets are melted extra water is added to the ocean (Greenland, Antartica, mountain glaciers)
181
How are greenhouse gases affecting sea level rise?
over 90% of heat trapped by greenhouse gases is being absorbed by the oceans, this makes water expand which results in sea level rise
182
How have sea levels changed around the world?
- Globally, sea levels have risen by 6cm
- doesn't happen at the same speed everywhere
- most places have seen a rise in sea level
- few places have seen a fall in sea level - waters have been cooling due to pacific decadal oscillation e.g. The Gulf stream, West Coast USA
- Western Pacific sea levels have been rising very rapidly due to the heat being pushed from east to west across the Pacific
183
What contributes to sea level rise?
- thermal expansion (40% so far)
- melting of glaciers e.g. Alps,Himalayas, Andes (27% so far)
- melting of major ice sheets e.g. Antarctic (10%), Greenland (15%)
184
Why is there a debate about how much sea levels will rise?
- unclear about how much temperatures will rise and therefore how much thermal expansion
- unclear to how rapidly the ice sheets will melt - Greenland ice sheet is more vulnerable than Antarctic as it is smaller and is not as close to the pole
185
Where is most at risk of sea level rise?
Low-lying areas - The Maldives, Bangladesh, Netherlands
| Coastal Cities - New York, Southampton, Mumbai, Tokyo, Miami
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What melts to create higher sea levels?
- glaciers, ice caps, ice sheets, thaws permafrost
| - more water is added to the oceans which creates a sea level rise
187
What is thermal expansion?
As seawater heats up by absorbing heat fro the atmosphere its volume expands
188
What have the IPCC projected?
-the projected rate of sea level rise is between 8-16mm per year
189
What impacts will further sea level rise have?
- wave heights will increase in the Arctic Ocean as sea ice melts, increasing wave erosion on Arctic coasts
- stormier seas - stronger storms such as mid-latitude depressions creating larger, more destructive waves
- these plus higher sea level rates makes it easy to predict that erosion rates and coastal change in general will increase in the future
190
Coastal flood risk
the risk or likelihood of flooding taking place at the coast
191
What are the factors influencing flood risk at the coast?
- eustatic sea level rise - caused by global warming
- dams
- population increase at the coast
- destruction of mangrove forests
- low-lying land
- shape of the coast
- groundwater extraction
- isotonic sinking
- global warming
192
How does eustatic sea level rise caused by global warming influence flood risk at the coast?
- it is predicted by IPCC that sea level will rise to be 28-98cm by 2100
- human and global
193
How does dams influence flood risk at the coast?
-block sediment getting to deltas to replace what is lost by erosion
local and human
194
How does population increase at the coast influence flood risk at the coast?
- by 2060, 12% will live in low elevation coastal areas
- this increases demand for water extraction which leads to more risk
- global and human
195
How does destruction of mangrove forests influence flood risk at the coast?
- this is done to provide wood and charcoal however it leaves the coast exposed to erosion
- mangroves can reduce wave heights by 40%, stabilises sediment and reduces storm surge height
- local and physical
196
How does low-lying land influence flood risk at the coast?
- especially islands like the Maldives and deltas like the Ganges and The Nile
- local and physical
197
How does the shape of the coast in Benegal influence flood risk at the coast?
The North Sea and the bay of Bengal
-the coast narrows, acting as a funnel for weather systems, increasing storm surges heights which is called the fuelling effect
198
How does groundwater extraction influence flood risk at the coast?
-can cause subsidence of land at the coast
199
How does isotonic sinking influence flood risk at the coast?
-causing south eastern Britain to sink
200
How does global warming influence flood risk at the coast?
-evidence that this will increase wind speeds, wave heights, frequency of storm surges and the magnitude of tropical storms
201
How does a storm surge form?
- low pressure weather event (depression) creates a bulge in the sea
- strong winds arrives a pushes the bulge towards the coast
- land topography can funnel the sea, increasing the height further
- high tides can also increase the height
- sea level rushes onto land as a surge
202
What are the elements for a storm surge to occur?
- low air pressure - zone of rising air that creates rain clouds
- strong winds
- very high tides
203
How have methods of measuring erosion changed through time?
- posts in the ground were used as reference points before GPS was invented in the 1990s
- old maps are used to look at changes before this
- Now LIDAR is used in combo with GPS
204
What does LIDAR stand for?
Lights detection and ranging
205
What is LIDAR?
A land bases laser scanner that takes several scans and combines information with GPS (Global positioning system/satellite
206
How does LIDAR work?
- equipment is set up on the beach in front of the eroding cliff line from at a distance of 100-150m
- it scans a swathe of cliff up to 800m in width, collecting 2000 individual measurements of the cliff per minute
- data collected in the filed by laser scanning and GPS are entered into a modelling package which calculates cliff top recession rates
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Physical factors causing coastal erosion
- geology of coast
- marine processes
- subaerial processes
- tides
- wind direction
- weather systems
208
Human factors causing coastal erosion
- coastal defences
| - offshore dredging
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Case Study: What happened to Hallsands Village?
| Which topic does this relate to?
- a storm ripped apart the village in 1917 because of the villages natural shingle beach defence was dredged in the 1890s out to create a new navel dock in Plymouth and there was nothing to dissipate the energy
- relates to what factors contribute to coastal recession
210
What are the social impacts of coastal flooding and recession?
- deaths
- health - stress and worry
- bereavement
- amenity value
211
What are the economic impacts of coastal flooding and recession?
- loss of property
- loss of businesses
- damage to infrastructure
212
What are the environmental impacts of coastal flooding and recession?
-loss of coastal ecosystems and habitats
213
Examples of social impacts of coastal flooding and recession
| -environmental refugees
-environmental refugees will be created in greater numbers as sea levels continue to rise and takes peoples homes
-developed countries need to offer their help to
environmental refugees from less developed countries
e.g - New Zealand has accepted 3000 people from Tuvalu as part of a labour migration plan
-most of the land in Tuvalu and the Maldives is only 2-3m above sea level
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Examples of environmental impacts of coastal flooding and recession
-fragile ecosystems
- as sea levels rise, salt water will be pushed higher up estuaries and damage fragile ecosystems
e. g. The Great Barrier Reef, Australia could perish as sea levels rise as they require a certain amount of light for photosynthesis
215
Examples of economic impacts of coastal flooding and recession
-environmental refugees
e. g. South Devon main railway line at Dawlish was destroyed in Feb 2014 by severe coastal storms £35m
e. g. the collapse of Holberk Hall Hotel in Scarborough 1993 after 2 months of heavy rainfall - no compensation was received
- homeowners on the Norfolk coastline have properties worth £1
- property insurance in the UK does not cover loss from coastal erosion - there is no compensation provided by the government
216
What is a refugee?
is someone seeking safety in another country due to fear of persecution in their own country
217
Sustainable
meeting the needs of today's coastal areas as well as those of the future
218
What is a major factor they need to consider when using sustainable coastal management?
-future sea level rise and erosion means adaptation in the best way to minimise impacts is the best way forward
219
Should coastlines be managed as a whole or in sections?
-better as a whole, taking into consideration each littoral cell and how they interlink (ICZM)
220
What kind of sustainable coastal management strategies could be used to help manage and adapt?
- educating communities on change
- monitoring coastal change
- creating alternative livelihoods
- managed retreat and soft engineering
221
What is sustainable management?
a long-term approach that considers future threats such as sea level rise and storm surges
-can sometimes result in the abandonment of coastline areas e.g. Island States or lowland areas
222
Why are their some conflicts with local people with sustainable coastal management?
- can sometimes result in the abandonment of coastline areas
- this will conflict with the wishes of local people who may lose their; land, home, job and sense of community
- may feel their is no social justice
223
What affects the coastal land?
- physical processes operating in a littoral cell which are interlinked for long stretches of the coast
- human activities
224
What factors need to be considered when managing coasts?
- the long length of coastline
- all stakeholders
- long timescale (physical processes can take 100s of years)
225
What does ICZM stand for?
integrated coastal zone management
226
What are the aims of ICZM?
- conservation of coastal ecosystems
- ensuring the ability of future generations to use the coast
- involvement of all stakeholders
227
What is the ICZM?
A systems perspective recognises that an action in one location is likely to have an impact elsewhere. The development of ICZM plans takes this as a basis for holistic (all components taken into account) planning.
228
Physical factors affecting coastal retreat
- geology of the coast
- marine processes
- sub-aerial processes
229
When will the most rapid retreat occur?
Where there are weakly consolidated rocks, large destructive waves, submergence of the coastline, large scale mass movements and constant weathering processes
230
What factors cause slow rates of recession?
- resistant rocks
- smaller constructive waves
- little mass movements
- slow weathering processes
231
What are the human factors that affect coastal recession?
- coastal defences
| - offshore dredging
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What are the human factors that affect coastal recession?
- coastal defences
- example
- built at one location will init the supply of sediment cell, this results in the coast further along won't receive beach building sediment
- when supply is cut off, the beach gets narrower which means it is less able to absorb wave energy which allows the waves to hit back-shore with more force
- e.g. Dunwhich, South of Southwold on Suffolk Coast
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What are the human factors that affect coastal recession?
- offshore dredging
- example
- removes sand and gravel for construction purposes to deepen entrances of ports or to supply sediments for beach nourishment
- deeper water caused by dredging allow waves to maintain their circular and energy closer inshore which as a destructive impact on the coast
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What impact does dredging have on the natural environment?
- removes benthic species and communities
- increases suspended sediment levels which damages coral reefs
- sediments settling and covering sub-tidal and intertidal marine communities
- increased deposition may raise sediment levels such as in estuaries
- artificial deposition on beaches may offer sea level rise or isostatic sinking
- local sea currents may be altered and waves may become much larger, affecting sediment balance and erosion rates
235
How do sub-areal processes affect coastal retreat?
- weathering weakens the rocks found at the coast and allows erosion rates to increase
- mass movement moves sediments to the base of coastal slopes where wave action and longshore drift can carry material away
- this then exposes the base of coastal slopes, resulting in cliffs retreating further
236
How does rainwater have a direct impact on coastal slopes?
-creates rills and then gullies in unconsolidated materials or at weak points in harder rock
237
How does wind direction affect coastal retreat?
- changes daily and determines wave direction
- strong winds = large waves
- coasts will experience maximum erosion at these times and less when winds come from another direction
- this links to fetch - the longer the fetch, the larger and more powerful the wave will be
- coasts with longer fetches will retreat faster than those with shorter fetches
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What is fetch?
- the distance from a coast across the ocean or sea to another coast
- gives the max distance that a wave can travel uninterrupted
239
What do high tides mean?
- spring tides
- occur hen the sun and the moon are aligned and so their total gravitational pull is at its strongest
- at high tides, waves are more likely to be able to reach the back-shore and erode the land faster
- if high tides coincide with destructive waves, erosion will be at a maximum.
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What do low tides mean?
- neap tides
| - occur when the sun and the moon are at right angles to each other and so their gravitational pull is at its weakest
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What are Perigean spring tides?
four times a year the moon is at its closest to the Earth and this creates slightly higher high tides
242
Describe a high pressure weather system
calm conditions
smaller waves
anticyclones
243
Describe a low pressure weather system
- mixture of air masses at different temperatures
- air rises rapidly
- strong winds rotating on an anticlockwise direction
- large waves created
244
Describe the wave systems in winter
- the difference between the temperature at the equator and the pole is at its greatest
- means the depressions are at their strongest
- with low air pressure and fast wind speeds
- creates large destructive waves which results in fast recession rates
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How does global warming have an impact on weather systems?
- has added more heat to the atmosphere - this has intensified the low-pressure systems
- means that the UK now experiences even stronger winds and larger waves during these storm events
- coastal erosion during winter is likely to increase, with recession being visible
246
What does the IPCC report on how global warming will impact weather systems?
-reports that a 1cm rise in sea level will erode a beach by about 1m horizontally as the balance of processes is altered
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What is hard engineering?
- the use of built structures
- it aims to protect the coast by working against the forces of nature
e. g. Groynes, Revetments, Rip Rap
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What is soft engineering?
- makes use of natural systems such as beaches, sand dunes and salt marshes to help with coastal defence
e. g. beach replenishment, offshore dredging
249
Hard engineering examples
```
groynes
revetments
gabion
rip rap
recurved sea wall
breakwaters
```
250
Soft engineering examples
- beach replenishment/nourishment
- cliff regrading
- cliff drainage
- dune restoration
- developing natural defences/managed retreat
251
What are groynes? pros
wooden or rock structures that are along the beach at right angles fro the coast
- they trap sediment moved by LSD and build up beach
- beach absorbs energy and increases recreational value
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Cons of groynes
- can starve areas down-drift of sediment
- wood rots
- rock is more expensive £1000 per linear metre
253
What are revetments? pros
Wooden or rock ramps that line the coast
- absorb wave energy
- air spaces allow the backwash of the wave to drain away but the sediment is trapped behind, reducing removal by destructive waves
254
Cons of revetments
- wood rots
- rock is more expensive £1500 per linear m
- don't cope well with powerful storm waves so need lots of maintenance
- unsightly
- reduces access to beach
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What are gabions? pros
Cages of small rocks, stacked to make a wall along the coast
- absorbs wave energy
- flexible as can be added in different places
- easy to maintain
256
cons of gabions
- light weight so can be removed in storms
- not suitable for high energy coasts
- cages can break and spill contents
- unsightly
257
What is rip rap? pros
large boulders positioned along the coastline
- large surface area so absorbs wave energy
- can be used to hold back mass movements
258
cons of rip rap
- expensive including transport costs £50 per cubic m
- can be. under scoured by strong backwash
- can be moved in strong storms
- unsightly, decreases access to beach
- erosion occurs on back-shore in storms
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What is a recurved sea wall? pros
concrete barrier that is curved to reflect the waves and their energy
- can be stepped to dissipate energy
- tops used as promenades
- long lasting
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Cons of recurved sea wall
- most expensive £5000 per linear m
- technical to build
- foundations can be undermined - lsd or destructive waves
- expensive to maintain
- causes coastal squeeze
- need deep foundations to prevent undercutting
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What are breakwater? pros
- granite rock boulder dropped and aligned in short lengths in shallow offshore waters parallel to the coast
- absorbs and dissipates waves before it reaches foreshore
- created sheltered areas for recreation and boats
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cons of breakwater
- expensive (1m -2m)
- unsightly at low tide as geology does not match
- may need further hard engineering
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What is beach replenishment? pros
- sand Is dredged from the sea bed and pumped onto the beach to replenish it from the effects of LSD or destructive waves
- the beach can be 'reprofiled' to recreate its original shape
- large beach absorbs wave energy
- natural looking
264
cons of beach replenishment
- need to be done every few years as lsd and destructive waves will continue to remove beach sediment
- can disrupt marine ecosystem or the natural sediment cycling and deepening offshore so waves have more energy
- expensive
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what is cliff regrading?
-engineers calculate a stable angle for the particular rock and the cliff is artificially cut back, changing its shape and reducing its angle to make it more stable
266
cons of cliff regrading
- very expensive £1m
- unnatural
- cliff line retreats into valuable land when constructed
- not full proof in extreme conditions
- needs agreement form land owners
267
What is cliff drainage?
pipes built through it to take out the water that has percolated through it
-this prevents the cliff becoming saturated and therefore, it is less likely to slump
268
cons of cliff damage
- unsightly
- can weaken the cliff when inserted
- cannot prevent weathering or subsequent rock fall
- difficult to insert enough without disturbing the cliff stability
269
What is dune restoration?
Geotextile netting can reduce erosion but still allow water in
- wooden structures erected vegetation planted to encourage sand deposition that builds up the dune
- boardwalks made for people so they do no trample sand dunes
- looks natural and protects ecosystems
270
cons of dune restoration
- only effective if public access controlled by fences and signs which reduces amenity value
- strong storms can cause damage
271
What is developing natural defences/managed retreat?
- natural ecosystems such as sand dunes and salt marshes help to stabilise coastlines and act as natural buffers against SLR and storms
- managed retreat also accepts that the coast is retreating by enhancing its natural defences, this can be slowed down
272
cons of developing natural defences/managed retreat
- needs agreement from land owners
| - doesn't prevent land from being lost
273
What are the 4 management options for shoreline management?
do nothing
hold the line
advance the line
managed retreat/realignment
274
do nothing
- no active intervention
| - meaning no investment will be made in coastal defences
275
hold the line
- trying to stop any further retreat of the coast
| - involves a mixture of hard and soft engineering techniques
276
advances the line
- involves reclaiming the land and building out into the sea
- may involve drainage as well as other hard engineering techniques
277
managed retreat/realignment
| example
removal of existing hard engineering defences and using more natural and sustainable techniques including protection, management or restoration of coastal ecosystems such as salt marshes and sand dunes
e.g. Abbots Hall Farm, Porlock Bay
278
What needs to be considered before making management decisions?
CBA - Cost benefit analysis
EIA - Environmental impact analysis
Technical feasibility
Social and political factors
279
What is a CBA?
Cost benefit analysis
- a tool to help decide whether defending a coastline from erosion and or flooding is worth it
- the value of the land vs the cost of the proposed management strategy
- looks at the properties and the businesses that would ve lost
280
What is an EIA?
Environmental impact analysis
- short or long term positive and negative impacts on environment
e. g. changes to flora and fauna, impacts on air and water quality
281
What is technical feasibility?
it is not possible to hold the line in all areas
| e.g. dynamic deposition features such as spits
282
What are the social and political factors considered before management decisions?
- impact and pressure on communities
- campaigning and loss pf property, businesses
- stress
283
Why is a CBA controversial?
- the value of a property is dependant on how at risk it is
- human costs (worry and stress) and environmental costs (value of biodiversity and scenic beauty) are hard to quantify in financial terms
284
What is the aim of EIA's?
- the aim is to identify the short term impact on the coastal environment of the construction
- and the long term impacts of building new sea defences or changing a policy from hold the line to no active intervention
285
What does an EIA include the assessment of?
- impacts of water movement and sediment flow which can affect marine ecosystems due to changes in sediment load
- impacts on water quality, which can affect sensitive marine species
- changes to flora and fauna including marine plants, fish, shellfish, marine mammals
- wider environmental impacts such as air quality, noise e pollution during construction
286
How has offshore dredging affected Winterton-on-sea and Lowestoft? - case study for coastal retreat
Research by Marinet shows that offshore dredging between 6-19km out to sea has resulted in beach loss, undermining of sand dunes and erosion of wind farm cables and support at Scroby Sands
287
How is Overstrand, North Norfolk being managed? - coastal retreat
- a full range of hard engineering coastal defences is in place protecting the cliff base from marine erosion
- the cliff still retreats as a result of rain entering the rock layers, increasing pore pressure and causing slumping
- leaves clear scars and terraces on the cliff face and lobes of clay across the promenade
288
Frost shattering/freeze thaw
| How does it work?
- mechanical
- only found on coasts in a climate where the temperature changes daily above and below zero
- water seeps into joints and cracks in the rock and when it freezes expands, entering pressure and forcing the rock apart
289
Frost shattering/freeze thaw
| What are the effects of it?
-angular rock fragments and a jagged cliff face are created, with scree slopes at the base
290
Salt crystaliszation
| How does it work?
- mechanical
- when waves break or splash cliffs on coastal rocks, the water evaporates, leaving behind sodium and magnesium salt compounds in joints and cracks in the rock
- these salt crystals grow and exert pressure and force the rock apart
- seawater may also enter porous rock and crystals grow inside the rock itself
291
Salt crystaliszation
| What are the effects of it?
- angular rock fragments are loosened and fall to create scree slopes at the base of the cliff or rock faces crumble away
292
Oxidation
| How does it work?
- chemical
- Oxygen combines with iron-based minerals in a rock, causing a chemical breakdown of the minerals, as shown by red-orange rusty colour on a rock face
293
Oxidation
| What are the effects of it?
- the rock minerals will no longer be bonded together and so the rock will crumble, making erosion easier
294
Seaweed acids
| How does it work?
- biological
- some seaweed cells (kelp) cells contain pockets of sulphuric acid, so when these cells break in contact with rock, the acid will dissolve some rock minerals
295
Seaweed acids
| What are the effects of it?
-rock minerals will no longer be bonded together and so parts of a rock will crumble, and these become points of greater erosion
296
Boring molluscs
| How does it work?
- biological
- many marine molluscs live on coastal rocks, scraping away at the rock surface to get food or boring a hole in the rock to make a home
- example is the Piddock, which has a shell with serrated cutting edges
297
Boring molluscs
| What are the effects of it?
- pebbles and rocks with holes bored into them are more easily moved around by the waves
- the holes also provide weak points for other weathering processes to act
298
mass movement types
mechanical
chemical
biological
299
mass movement - mechanical processes
- freeze thaw
- salt crystaliszation
- wetting and drying
300
mass movement - mechanical processes
| - freeze thaw explanation
Water gets into cracks, freezes and expands by up to 9%. This exerts pressure on the cracks which loosens and breaks apart rock. Most vulnerable are well jointed rocks. Only happens when daily temperatures fluctuate around zero degrees
301
mass movement - mechanical processes
| - freeze thaw effects
Creates angular rock fragments at the base of cliffs called scree and a jagged cliff face. Also can contribute to large rock falls.
302
mass movement - mechanical processes
- freeze thaw
- vulnerable rocks
- any rocks with cracks and fissures, especially high up cliffs away from salt spray
- freezing is relatively uncommon on UK coasts, especially in south and salt spray can reduce its effect even further
303
mass movement - mechanical processes
| salt crystallisation
- Salt spray or waves hitting cliffs make them wet with seawater.
- This evaporates and leaves salt in cracks on the cliff. Over time, salt crystals form and grow, exerting pressure on the cracks and pores which loosens and breaks apart rock.
304
mass movement - mechanical processes
salt crystallisation
effects
Creates angular rock fragments at the base of cliffs called scree. Some rock faces crumble away.
305
mass movement - mechanical processes
salt crystallisation
-most vulnerable rocks
Most vulnerable are well jointed rocks (limestone) and porous rocks (Sandstone, chalk). Happens most in hotter climate.
306
mass movement - mechanical processes
wetting and drying
explanation
Rocks rich in clay expand when they get wet and contract when they dry. This repeated process causes them to crack and break apart.
307
mass movement - mechanical
wetting and dryingprocesses
effects
Cracks form in cliffs so they become vulnerable to slumping.
308
mass movement - chemical processes
- carbonation
- oxidation
- hydrolysis
309
mass movement - chemical processes
-carbonation
explanation
Limestone slowly dissolves as it reacts with weak carbonic acid in rainwater.
310
mass movement - chemical processes
- carbonation
- effects
Joints and cracks get wider on cliffs and wave cut platforms. This makes them more vulnerable to other weathering and mass movement processes.
311
mass movement - chemical processes
- carbonation
- most vulnerable rocks
limestone and other carbonate rocks
312
mass movement - chemical processes
- hydrolysis
- explanation
the breakdown of minerals to form new clay minerals, plus materials in solution, due to the effect of water and dissolved co2
313
mass movement - chemical processes
- hydrolysis
- vulnerable rocks
igneous and metamorphic rocks containing feldspar and other silicate minerals
314
mass movement - chemical processes
- oxidation
- explanation
-Oxygen combines with iron based minerals in a rock causing a chemical breakdown of the minerals shown by a red rusty colour on the rock face. Sandstones and shales often contain iron so are vulnerable.
315
mass movement - chemical processes
- oxidation
- effect
Leads to crumbling of the cliff as sections are no longer bonded together.
316
mass movement - chemical processes
- oxidation
- most vulnerable rocks
Sandstones, siltstones and shales often contain iron so are vulnerable as they can be oxidised
317
mass movement - biological processes
- plant roots
- rock boring
- seaweed acids
318
mass movement - biological processes
- plant roots
- explanation
-Tree and plant roots growing into cracks can slowly widen them and cause them to break apart. Important process on vegetated rock faces.
319
mass movement - biological processes
- plant roots
- effects
Can cause rock falls
320
mass movement - biological processes
- plant roots
- most vulnerable rocks
an important process on vegetated cliff tops that can contribute to rockfalls
321
mass movement - biological processes
- rock boring
- explanation
-Clams and molluscs bore (dig) into rock to make their homes. They can also secrete acids that dissolves rocks. Sedimentary rocks in the intertidal zone are vulnerable.
322
mass movement - biological processes
- rock boring
- effects
Holes and weaknesses created are vulnerable to erosion and further weathering.
323
mass movement - biological processes
- rock boring
- most vulnerable rocks
Sedimentary rocks in the intertidal zone are vulnerable.
324
mass movement - biological processes
- seaweed acid
- explanation
Some seaweed species like kelp contain pockets of sulphuric acid that can burst on rocks and dissolve them.
325
mass movement - biological processes
| -effects
Leads to crumbling of the cliff as sections are no longer bonded together
326
What are the different classifications of mass movement?
-Fall
-topple
-translational slide
rotational -slide/slumping
flow
327
What are the different classifications of mass movement?
| -fall
- rockfalls or blockfalls, are a rapid form of mass movement
- on coasts blocks of rock can be dislodged by mechanical weathering or by hydraulic action erosion
- undercutting of cliffs by the creation of wave-cut notches can lead to large falls
328
What are the different classifications of mass movement?
| -topple
- geological structure influences topples
- where rock strata have a very steep seaward dip, undercutting by erosion will quickly lead to instability and blocks of material toppling seaward
329
What are the different classifications of mass movement?
| -translational slide
- a very low angle seaward dip in strata will prevent falls
| - material will tend to slide down the dip slope towards the sea
330
What are the different classifications of mass movement?
| -rotational slide/slumping
- mass movements can occur along a curved failure surface
- huge masses of material can slowly rotate downslope over periods lasting from days to years
- water plays an important role in rotational slides
331
What are the different classifications of mass movement?
| -flow
- flows are common in weak rocks such as clay or unconsolidated sands
- these materials can become saturated, lose their cohesion and flow downslope
- heavy rainfall combined with high tides can contribute to saturation
